Field of the Invention
The present invention relates to an organic light emitting device using an organic electroluminescence element.
Description of the Related Art
In recent years, printers employing a laser scanning system based on an electrophotographic technology are widely spread. In a general laser beam printer, light emitted from a laser light source is scanned by a scanning unit to expose a photosensitive member to light. Downsizing of the laser scanning unit is difficult due to its structure.
Besides, there has been investigated an LED printer method employing a system of exposing the photosensitive member to light with use of an elongated exposure light source (light emitting device: LED) including light emitting elements arranged in a row. This method enables the light source unit to be downsized, and hence this method is effective for downsizing the printer apparatus. Further, among the LEDs, in particular, an organic electroluminescence element (hereinafter referred to as “organic EL element”) is a light emitting element having high definition and low power consumption, and thus is suitably used as a light emitting device for a light source unit of a printer apparatus. In Japanese Patent Application Laid-Open No. 2010-280066, there is disclosed an image forming apparatus using organic EL elements as the exposure light source.
The organic EL element is a sophisticated light emitting element, but it is known that its characteristic may be degraded due to moisture. Meanwhile, in order to produce a larger number of organic light emitting devices from one mother glass substrate for productivity enhancement, the substrate size per organic light emitting device is preferred to be as small or thin as possible. Therefore, the width of a region called a frame region, which is present at the end of the substrate and is outside of a region in which light emitting pixels are formed, is preferred to be as narrow as possible. However, in this case, there is a fear of reduction in sealing performance at the end of the substrate. Therefore, in order to maintain the light emitting performance of the organic EL element, it is important to consider how to suppress moisture intruding into the organic EL element from the end of the substrate.